Unless you can find an Akai Deep IMpact then the BassMicroSynth is the way to go especially for square wave sounds. It has the square wave and also the octave up with square wave plus you can add in bass and sub bass tones to enrichen your sound as well as full control over the adsr functions. It can be a drag to use live if you need to change sounds but once you learn all your settings it is a wonderful sound tool.
The down side is it is a fragile pedal that you will need to protect and it does not have true bypass. When I use mine live it is in a loop and sits where I can easily reach it to make adjustments. I use it quite a lot for recording because I can easily slide in just the sound I want.
IMO the Boss is a complete waste of time unless you really love the sound and honestly there are several other pedals from Ibanez, Digitech and even many multiefx pedals that have more useful synthy tones than the Boss, shux I even use some of the synth sounds on my Zoom 607 from time to time especially the Taurus setting.

in terms of the comments about the tweakability and true bypass, for either pedal, i was thinking of having it higher up (keyboard stand possibly?) and having a loooper on the ground near it so i can just stomp the switch and have the pedal going.

then if i need to have some tweaks i can sustain the note or whatever with my left hand and use my right to move the sliders. i guess i can even put little stickers to mark settings and all that for songs.